1. Technical Field
The present invention relates generally to a semiconductor memory device, and more particularly, to a semiconductor memory apparatus having pads.
2. Related Art
Generally, differential signaling is used in the transmission of data between a high-speed circuit and a high-speed interface, that is, a central processing unit (CPU), a controller, a system interface, etc. In differential signaling, information is transmitted electronically using a differential signal composed of two complementary signals, for example, a positive signal (hereinafter, designated as a “+” signal) and a negative signal (hereinafter, designated as a “−” signal). In greater detail, the “−” signal of the differential signal is designed and generated to have a reverse phase of the “+” signal level. Therefore, even when a positive signal having a low level is applied, data signals that are stable can be transmitted by the difference between the positive signal and the negative signal having the reverse phase thereto. With this in mind, it can be understood that accurately maintaining a cross point of output voltage ‘Vox’ between the differential signals is an important factor to maintain the differential characteristics of the signal. Differential signal lines carrying the complementary signals are connected to chip pads. To support an accurate cross point, the chip pads (i.e., differential signal pads) and differential signal lines connected to the differential signal pads are arranged adjacent to each other so that the distance between the chip pads and the signal lines is substantially the same. This arrangement helps to reduce mismatching between the signals.
Meanwhile, high speed transmission in a semiconductor device requires an increased operation frequency, which in turn leads to increased power consumption. As a consequence, a larger number of external supply power pads and ground power pads are provided to stably supply power.
In this case, the arrangement of the pads applied with the differential signals and the power pads is very important in the high-speed operation circuit. For example, when a connection line between the pad applied with the positive signal and an external supply power pad is longer than a connection line between the pad applied with the negative signal and an external supply power pad, the effective termination resistance ‘RTTeff’ becomes mismatched. Therefore, even if the positive signal line and the negative signal line are disposed to be adjacent to each other on the semiconductor circuit substrate, the cross point of the output voltage between the positive signal and the negative signal can change due to a mismatch of the effective termination resistor. Consequently, a mismatching phenomenon between the positive and negative signals can occur.